Description

The objective of this technique is to provide a semantic grouping for related form controls. This allows users to understand the relationship of the controls and interact with the form more quickly and effectively.

Form controls can be grouped by enclosing them with the fieldset element. All controls within a given fieldset are then related. The first element inside the fieldset should be a legend element, which provides a label or instructions for the group. Fieldsets can be nested if desired, although this can lead to confusion if overdone.

Grouping controls is most important for related radio buttons and checkboxes. A set of radio buttons or checkboxes is related when they all submit values for a single named field. They work in the same way as selection lists, allowing the user to choose from a set of options, except selection lists are single controls while radio buttons and checkboxes are multiple controls. Because they are multiple controls, it is particularly important that they be grouped semantically so they can be more easily treated as a single control. Often, user agents will present the value of the legend before the label of each control, to remind users that they are part of the same group.

It can also be useful to group other sets of controls that are not as tightly related as sets of radio buttons and checkboxes. For instance, several fields that collect a user's address might be grouped together with a legend of "Address".

Authors sometimes avoid using the fieldset element because of the default display in the browser, which draws a border around the grouped controls. This visual grouping is also useful and authors should seriously consider retaining it (or some form of visual grouping). The visual effect can be modified in CSS by overriding the "border" property of the fieldset and the "position" property of the legend.

Examples

Example 1: A multiple choice test

This example shows a test item with one question and five possible answers. Each
answer is represented by a radio button (input type="radio"). The radio
buttons are contained within a fieldset. The test question is tagged
with the legend element.

Example 2: A set of checkboxes

The User Profile page for a Web site allows users to indicate their interests by
selecting multiple checkboxes. Each checkbox (input type="checkbox")
has a label. The checkboxes are contained within a
fieldset, and the legend element contains the prompt for
the entire group of checkboxes.

Example 3: Radio buttons submitting to the same named field

This example requests the user to choose a single philosopher. Note that each field has the same "name" attribute, indicating these radio buttons are related (they all submit the same field), and should be grouped as shown. Also note that while the "name" attributes are the same, the "id" attributes must be unique.